In many industrial processes, a by-product fluid (air or water) stream contaminated with minor amounts of condensable organics (i.e. vapors or liquids) is produced. For ecological reasons, it is not desirable to simply discharge these contaminated streams to the environment, especially if the type and amount of organics exceeds legal thresholds. Furthermore, it may be economically beneficial to separate the organics from the stream so that they can be recycled or otherwise disposed. Accordingly, there is a need for separating organics from by-product streams.
One approach to the solution of the organic separation problem is the use of a membrane technology. Katoh, M., et al., "Hydrocarbon Vapor Recovery with Membrane Technology", NKK Technical Review, Vol. 56, (1989) pp. 67-72. This approach involves a composite membrane having a permselective layer, a porous (microporous) membrane layer, and a supporting fabric. The composite membrane is in the form of a flat sheet. The composite membrane is wound to form a spiral wound module. The permselective layer is described as being ultra thin (several microns) and selectively permeating hydrocarbon or other organic vapors. The chemical composition of the permselective layer is not disclosed.
In view of the foregoing, there is a need to identify materials for use as the permselective material for removing organic vapors for effluent streams.
Poly (alkyl sulfone)s are known. See: U.S. Pat. Nos. 3,928,294 and 4,179,757; Concise Encyclopedia of Polymer Science and Engineering, John Wiley & Sons, New York City, N.Y. (1990) pp. 674-676; Kirk-Othmer Encyclopedia of Chemical Technology, 3rd Edition, John Wiley & Sons, New York City, N.Y. (1983) Vol. 21, page 966; Gray, D. N., "Olefin/Sulfur Dioxide Copolymers", Polymer News, Gordon and Breach Science Publisher, Inc., Vol. 3 (1976), pp. 144-146; Gray, D. N., "The Status of Olefin-SO.sub.2 Copolymers as Biomaterials", Biomedical and Dental Applications, Plenum Publishing Corporation, New York City, N.Y. (1981) pp. 21-26; and Gray, D. N., "Polymeric Membranes for Artificial Lungs", American Chemical Society (1984).
Ultra thin poly (alkyl sulfone) coatings on microporous polypropylene (e.g., CELGARD.RTM. membranes) are known. See: Gray, "The Status . . . ", Ibid., page 24. The permselectivity (or selectivity) of that composite membrane is 4.1.